1. Field of the Invention
The present invention pertains to a lubricant leakage stop employed with an electric motor. More specifically, the present invention pertains to an annular groove that is formed into the exterior surface of a horizontally oriented motor shaft just outside of a bearing assembly supporting the shaft but within the lubrication system surrounding the bearing assembly. In one embodiment the annular groove is formed with an annular inner surface at the bottom of the groove and with an annular intermediate surface positioned between two portions of the annular inner surface. The intermediate surface has a larger diameter dimension than the two inner surface portions of the groove on the axially opposite sides of the intermediate surface. The intermediate surface also has a smaller diameter dimension than that of the two outer surface portions of the shaft on axially opposite sides of the groove. In a second embodiment, the annular groove is formed with an annular inner surface that tapers from the bottom of the groove outwardly to the outer surface portion of the shaft on one side of the groove. Any lubricant leakage axially along the shaft is stopped by the annular groove and is thrown by rotation of the shaft radially outwardly from the intersection of the shaft outer surface and the groove of both embodiments, or from the intersection of the shaft intermediate surface and the groove in the first embodiment. The lubricant thrown radially outwardly by the shaft rotation is thrown to the fibrous, lubricant impregnated material of the bearing lubrication system that surrounds the shaft and the bearing supporting the shaft and is returned by the material to the bearing.
2. Description of the Related Art
Home appliance motors, for example electric motors used in electric household appliances like dishwashers, clothes washers, and clothes dryers, often have horizontally oriented rotating shafts that are typically mounted in sleeve bearings or porous sintered metal bearings where bearing surfaces support the shafts for rotation. The bearings are typically mounted in end shields of the electric motor housing. A bearing cap is mounted in the end shield shaft opening and surrounds the bearing and a lubricant-permeated fibrous material is packed inside the bearing cap surrounding the bearing.
The lubricant-permeated fibrous material provides a self-contained source of lubricant to the motor shaft bearings. The material is packed around the bearing, contacting the bearing exterior surface, and the lubricant permeating the material passes through the porous bearing to the bearing surface supporting the shaft for rotation. In this manner, lubricant is supplied to the interface of the shaft exterior surface and the bearing surface.
Because the bearing lubrication system described above is self-contained, loss of lubricant from a motor employing the lubrication system can have serious consequences on the motor""s operational life. One of the major causes for sleeve bearing failures is loss of oil out of the bearing lubrication system. Sleeve bearings by design experience some oil leakage out of the motor along the shaft exterior surface that interfaces with the bearing surface of the bearing.
To combat this problem, annular obstructions have been positioned on the shaft adjacent the bearing, where the obstruction would stop the leakage of lubricant along the shaft and on rotation of the shaft would sling or throw the leaking lubricant radially outwardly toward the fibrous material packed around the shaft. Prior art annular obstructions employed on a motor shaft include a single annular groove formed in the shaft exterior surface, an annular neck formed on the shaft exterior surface, or a rubber washer positioned on the shaft exterior surface. However, none of these prior art methods for stopping oil leakage along the shaft were 100% effective. In addition, the annular groove shaft was disadvantaged in that the groove formed sharp annular corners at the shaft exterior surface on the axially opposite sides of the groove. These sharp annular corners could damage some parts that were press fit on the shaft over the groove, for example, plastic cooling fans and plastic thrust washers for the bearing assembly.
What is needed to overcome the disadvantages of prior art lubricant leakage stops discussed above is a lubricant leakage stop for a rotating shaft that reliably stops lubricant from leaking axially over the shaft exterior surface and does not damage component part of the rotary device that are press fit on the shaft and passed over the lubricant leakage stop.
The lubricant leakage stop of the present invention overcomes the shortcomings of the prior art leakage stops employed on horizontally oriented shafts by providing an annular groove on a shaft with a novel configuration that reliably stops lubricant leakage axially across the shaft exterior surface and does not damage component parts of a rotary device press fit on the shaft and passed over the annular groove.
The shaft of the invention has an axial length and a center axis of rotation extending between opposite first and second ends of the shaft. The electric rotary device, for example an electric motor, is mounted on an intermediate portion of the shaft between its opposite ends. The device is contained in a housing. A pair of bearings mounted in axially opposite ends of the housing support the shaft for rotation in the housing. The first end of the shaft projects axially from one of the bearings and the housing interior. The opposite second end of the shaft is typically mounted in the second bearing and is contained in the housing. However, if the second end of the shaft also projects from the housing interior, the lubricant leakage stop of the invention would be employed on both the first and second ends of the shaft.
In the illustrative embodiment of the invention, the lubricant leakage stop is employed only on the first end of the shaft. The stop is basically an annular groove of novel configuration formed in the exterior or outer surface of the shaft adjacent the bearing at that end of the shaft and inside the lubricant-permeated fibrous material of the bearing lubrication system. The annular groove is formed in the shaft where portions of the shaft outer surface on axially opposite sides of the groove have the same outer diameter dimension.
In a first embodiment, the groove of the lubrication stop is formed in the shaft with an annular shaft interior or inner surface at the bottom of the groove. On one axial side of the groove a first radial surface extends from the inner surface of the groove radially outwardly to the shaft outer surface. The first radial surface intersects the shaft outer surface at an annular, right angle corner. At the axially opposite end of the groove, a second radial surface extends from the groove inner surface radially outwardly to the shaft outer surface. The second radial surface intersects the shaft outer surface at an annular, chamfered corner.
An annular intermediate surface of the shaft is positioned in the groove, with portions of the groove inner surface positioned on axially opposite sides of the intermediate surface. The shaft intermediate surface has a diameter dimension that is larger than the diameter dimensions of the two portions of the groove inner surface on the axially opposite sides of the intermediate surface, but is smaller than the diameter dimension of the two portions of the shaft outer surface on the axially opposite sides of the groove. A third radial surface extends radially outwardly from the groove inner surface to the shaft intermediate surface and a fourth radial surface extends radially outwardly from the groove inner surface to the shaft intermediate surface on axially opposite sides of the intermediate surface. Both the third and fourth radial surfaces intersect the shaft intermediate surface at an annular, right angle corner.
The shaft intermediate surface being positioned in the annular groove between two portions of the groove inner surface divides the groove into two groove sections, each positioned on an axially opposite side of the intermediate surface. The double groove sections of the lubricant leakage stop are more effective at stopping leakage from the motor along the shaft outer surface than the prior art annular groove. Any lubricant that leaks along the shaft outer surface and manages to cross the first groove section to the shaft intermediate surface is stopped from travelling axially along the shaft by the second groove section. The sharp, annular, right angle corners of the intermediate surface also function to sling or radially throw lubricant off the intermediate surface toward the lubricant-permeated fibrous material of the bearing lubrication assembly when the shaft is rotated.
Because the annular intermediate surface of the shaft has a smaller diameter than the diameter dimension of the shaft outer surface on opposite sides of the groove, component parts press fit over the shaft outer surface will pass over the shaft intermediate surface without being damaged by the sharp annular, right angle corners of the shaft intermediate surface. In addition, the component parts will pass over the annular groove and onto the shaft outer surface on the opposite side of the groove with the annular, chamfered corner at the opposite side of the groove preventing any damage to the component parts.
In a second embodiment, the groove of the lubrication stop is formed in the shaft by a pair of radial surfaces. On one axial side of the groove a first radial surface extends from the bottom of the groove radially outwardly to the shaft outer surface. The radial surface is perpendicular to the shaft center axis and intersects the shaft outer surface at an annular, right angle corner. At the axially opposite side of the groove, a second radial surface extends from the first radial surface at the bottom or interior of the groove radially outwardly to the shaft outer surface. The second radial surface has a tapered, curved or conical configuration that extends radially outwardly from the first radial surface as it extends axially away from the first radial surface. The second radial surface intersects the shaft outer surface forming an annular, chamfered corner. The interior or bottom of the groove is formed by the intersecting circular edges of the first radial surface and the second radial surface.
Any lubricant that leaks along the shaft outer surface is stopped from travelling axially along the shaft by the first radial surface of the groove. The sharp, annular, right angle corner of the intersection of the first radial surface with the shaft outer surface functions to sling or radially throw lubricant off the shaft toward the lubricant-permeated fibrous material of the bearing lubrication assembly when the shaft is rotated.
In addition, component parts press fit over the shaft outer surface will pass over the intersection of the first radial surface and the shaft outer surface without being damaged by the sharp, annular, right angle corner of the intersection. The component parts will pass over the annular groove and onto the shaft outer surface on the opposite side of the groove with the annular, chamfered corner between the second radial surface and the shaft outer surface at the opposite side of the groove preventing any damage to the component parts.
Thus, the lubricant leakage stops constructed as described above overcome the problem of lubricant leakage along the surface of a horizontally oriented shaft and the problem of damaging component parts of the electrical device that are press fit over the shaft and passed over the annular groove.